This investigation concerns a vital but little-studied aspect of auditory cognition and communication: the significance of subcategorical rhythmic patterning (i.e., timing and intensity microstructure) in conveying structure and expression. In music, these systematic variations give a "living quality" to the sound structures and engage the listener's attention and emotions. Thus they are an essential ingredient of expert performance. The proposed research has two general aims. The first aim (Parts 1 and 2) is to tap into listeners' cognitive representation of microstructure and study its dependence on both the musical structure and on listeners' musical experience. To this end, listeners' sensitivity to local and global changes in microstructure will be tested in high- uncertainty detection and discrimination tasks using meaningful musical materials -- conditions under which top-down expectations are likely to influence perceptual accuracy. The second aim (Part 3) is to reveal the factors underlying microstructural variation in performance, the psychological dimensions along which different performances are distinguished, and the relations between the two. This work involves the microstructural analysis of a number of expert piano performances, the evaluation of these (as well as other, experimentally manipulated) performances by musically experienced listeners, and the multidimensional and cross-correlational statistical analysis of the resulting data. By elucidating some of the principles that govern music performance, perception, and evaluation, these experiments will enhance our general understanding of the cognitive representation of hierarchically organized structures, of the nature of artistic communication, and of the objective basis of aesthetic judgment. In the long run, this research may suggest ways of improving music education and increasing music appreciation, with positive consequences for mental health and quality of life.